Gas chromatographic mass spectrometers (GC/MS) are formed of a gas chromatographic apparatus and a mass spectrometer. As a result, first, substances to be measured included in a substance (sample) that is the object of analysis are separated along the time axis in a gas chromatographic apparatus (GC). Next, the respective substances to be measured separated along the time axis are measured using a mass spectrometer (MS) so that the substances to be measured are separated according to the mass number so as to be detected. This measurement is repeated with short time intervals so that a number of mass spectra having the mass number along the lateral axis and the ion intensity along the longitudinal axis are prepared. In addition, the peak of a certain mass number is focused for each of the mass spectra, and the focused peaks are aligned along the time axis so that a mass chromatogram is prepared. Furthermore, all the peaks appearing in one mass spectrum are integrated, and they are aligned along the time axis so that a total ion chromatogram is prepared.
Thus, the substance to be measured is quantitated on the basis of the area and the height of the peaks appearing in this mass chromatogram and the total ion chromatogram. At this time, a standard substance of which the concentration is known in advance is introduced into a GC/MS in order to carry out quantification, and the calibration curve, which is prepared on the basis of the relationship between the gained peak area or height and the concentration as a result of the measurement, is used.
It is necessary, however, to measure a standard substance under certain conditions for measurement in order to prepare a calibration curve for every GC/MS apparatus. Therefore, a method for identifying and quantitating multiple components for general purposes in a GC/MS according to which a substance to be measured can be quantitated irrespective of the GC/MS used is disclosed (see, for example, Patent Document 1). This method for identifying and quantitating multiple components for general purposes collectively includes the database storing step of storing a database with which a relative calibration curve indicating the relationship between the peak area ratio in the chromatogram for the standard substance and the internal standard substance and the concentration ratio of the standard substance to the internal standard substance is registered (see FIG. 3), the measurement step of measuring an internal standard substance of which the concentration is known and a substance to be measured at the same time so that the mass spectra of the internal standard substance and the substance to be measured are gained, the calculation step of calculating the peak area ratio of the substance to be measured to the internal standard substance by preparing a chromatograph on the basis of the mass spectrum of the internal standard substance having a predetermined concentration and the mass spectrum of the substance to be measured, and the substance to be measured concentration calculating step of calculating the concentration of the substance to be measured on the basis of a relative calibration curve.
In accordance with this method for quantitating a substance to be measured, the concentration of the substance to be measured can be calculated using a relative calibration curve on the basis of the peak area ratio of the substance to be measured to the internal standard substance that is measured at the same time as the substance to be measured, and therefore, it is not necessary to prepare a calibration curve in advance by measuring the standard substance under certain conditions for measurement for every GC/MS used.
Here, the internal standard substance is selected from stable isotope compounds and compounds having similar chemical and physical properties of which the response to a GC/MS is similar to that of the substance to be measured and which can be measured separately from the substance to be measured. Deuterium bodies (D bodies), where hydrogen atoms are substituted with deuterium atoms, can be cited as examples.
In addition, chemicals substances including environment polluting substances, such as PCB, residual pesticides in foods and misused chemicals, can be cited as the standard substance.    Patent Document 1: Japanese Unexamined Patent Publication 2003-139755